Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 9, NWS Chicago, IL

August 25, 2021Cook County, DuPage County, Illinois

NWS Chicago, IL issued this flash flood warning at Aug 25, 2021, 7:21 PM CDT for Cook County, DuPage County, Illinois. It was in force for 3 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 25, 2021, 7:21 PM CDT (00:21 UTC)
Expired: Aug 25, 2021, 10:30 PM CDT
In force: 3 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Cook County, IL, DuPage County, IL

The radar

The Chicago radar (KLOT), 33 km from the middle of the area, began a volume at 00:24 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Aug 25, 7:30 PM CDT	FLOOD	1 Ese Darien, IL	6 INCHES OF STANDING WATER AT 79TH STREEET AND FARMINGDALE DRIVE IN DARIEN.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 0.4 hours before the alert went out and 200 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 2295 J/kg
Mixed-layer CIN: -13 J/kg
Mixed-layer LCL: 1479 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 51 m²/s²
0-3 km storm-relative helicity: 40 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

877 
WGUS53 KLOT 260021
FFWLOT
ILC031-043-260330-
/O.NEW.KLOT.FF.W.0009.210826T0021Z-210826T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Chicago IL
721 PM CDT Wed Aug 25 2021

The National Weather Service in Chicago has issued a

* Flash Flood Warning for...
  Central Cook County in northeastern Illinois...
  Eastern DuPage County in northeastern Illinois...

* Until 1030 PM CDT.

* At 721 PM CDT, doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Water was beginning to flood roadways 
  in parts of Darien.

  HAZARD...Flash flooding.

  SOURCE...Radar.

  IMPACT...Rapid-onset flooding of small creeks and streams,
           urban areas, highways, streets and underpasses, as
           well as other poor drainage and low lying areas.

* Some locations that will experience flash flooding include...
  Chicago, Cicero, Arlington Heights, Schaumburg, Des Plaines, Oak 
  Lawn, Berwyn, Mount Prospect, Wheaton, Hoffman Estates, Oak Park, 
  Downers Grove, Glenview, Elmhurst, Lombard, Ohare Airport, 
  Streamwood, Carol Stream, Hanover Park and Park Ridge.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4207 8817 4206 8784 4180 8776 4165 8776
      4166 8800

FLASH FLOOD...RADAR INDICATED

$$

Birk

2 follow-up statements

791 
WGUS73 KLOT 260109
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
809 PM CDT Wed Aug 25 2021

ILC031-043-260330-
/O.CON.KLOT.FF.W.0009.000000T0000Z-210826T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-DuPage IL-
809 PM CDT Wed Aug 25 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1030 PM CDT THIS 
EVENING FOR CENTRAL COOK AND EASTERN DUPAGE COUNTIES...

At 809 PM CDT, doppler radar continued to indicate scattered 
thunderstorms producing heavy rain across portions of the warned 
area. Between 1 and 3 inches of rain have fallen. Additional 
rainfall amounts of 1 to 2 inches are possible in the warned area 
early this evening. Flooded roads have been reported in and around 
Darien.

HAZARD...Flash flooding.

SOURCE...Radar.

IMPACT...Rapid-onset flooding of small creeks and streams, urban
         areas, highways, streets and underpasses, as well as
         other poor drainage and low lying areas.

Some locations that will experience flash flooding include...
Chicago, Cicero, Arlington Heights, Schaumburg, Des Plaines, Oak 
Lawn, Berwyn, Mount Prospect, Wheaton, Hoffman Estates, Oak Park, 
Downers Grove, Glenview, Elmhurst, Lombard, Ohare Airport, 
Streamwood, Carol Stream, Hanover Park and Park Ridge.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4207 8817 4206 8784 4180 8776 4165 8776
      4166 8800

FLASH FLOOD...RADAR INDICATED

$$

Birk

913 
WGUS73 KLOT 260333
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
1033 PM CDT Wed Aug 25 2021

ILC031-043-260343-
/O.EXP.KLOT.FF.W.0009.000000T0000Z-210826T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-DuPage IL-
1033 PM CDT Wed Aug 25 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR CENTRAL COOK AND EASTERN 
DUPAGE COUNTIES...

The threat of widespread heavy rain is ended. Therefore significant 
flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

LAT...LON 4207 8817 4206 8784 4180 8776 4165 8776
      4166 8800

$$

Birk

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 25, 7:33 PM CDT	Special Marine Warning	LOT		117 min
Aug 25, 8:34 PM CDT	Areal Flood Advisory	LOT	Cook, Kankakee, Will	3 hr
Aug 25, 8:43 PM CDT	Special Weather Statement	LOT	Kankakee	47 min
Aug 25, 8:54 PM CDT	Areal Flood Advisory	LOT	DuPage, Kane, Kendall, Will	17 min
Aug 25, 9:06 PM CDT	Flash Flood Warning	LOT	DuPage, Kane, Kendall, Will	5 hr
Aug 25, 9:15 PM CDT	Flash Flood Warning	LOT	Cook, Kankakee, Will	4 hr
Aug 26, 1:38 AM CDT	Areal Flood Advisory	LOT	Kane, Kendall	2 hr
Aug 26, 5:30 PM CDT	Special Weather Statement	LOT	Cook	30 min

Nearby

Flash Flood Warnings in Illinois, 2021 Every flash flood warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.